面試題18：順時針打印矩陣

分析：把矩陣想象成若干個圈，用一個循環打印矩陣，每次打印矩陣的一個圈

#include "stdafx.h"
#include <iostream>
using namespace std;

void PrintMatrixIncircle(int **nArr, int rows, int columns, int nStart)
{
	int nEndX = columns - 1 -nStart;
	int nEndY = rows - 1 -nStart;
	//從左到右打印一行
	for (int i=nStart; i<=nEndX; i++)
	{
		cout << nArr[nStart][i] << " ";
	}

	//從上到下打印一列
	if (nEndY > nStart)
	{		
		for (int j=nStart+1; j<=nEndY; j++)
		{
			cout << nArr[j][nEndX] << " ";
		}
	}
	
	//從右到左打印一行
	if (nEndY > nStart && nEndX > nStart)
	{		
		for (int t=nEndX-1; t>=nStart; t--)
		{
			cout << nArr[nEndY][t] << " ";
		}
	}

	//從下到上打印一列
	if (nEndY -1 > nStart && nEndX > nStart)
	{		
		for (int n=nEndY-1; n>=nStart+1; n--)
		{
			cout << nArr[n][nStart] << " ";
		}
	}	
}

//順時針打印矩陣，行數為rows，列數為columns
void PrintMatrixClockWisely(int **nArr, int rows, int columns)
{
   if (nArr == NULL || rows <= 0 || columns <= 0)
   {
	   return;
   }

   int nStart = 0;
   while (rows>(nStart*2) && columns>(nStart*2))   
   {
	   PrintMatrixIncircle(nArr, rows, columns, nStart);
	   nStart++;
   }
}


int _tmain(int argc, _TCHAR* argv[])
{
	int nMatrix1[4][4] = {{1,2,3,4},{5, 6, 7, 8},{9, 10, 11, 12},{13, 14, 15, 16}};
	int **pp1 = new int*[4];
	for (int i=0; i<4; i++)
	{
		pp1[i] = nMatrix1[i];
	}
	PrintMatrixClockWisely(pp1, 4, 4);
	cout << endl;

	int nMatrix2[1][4] = {{1,2,3,4}};
	int **pp2 = new int*[1];
	for (int i=0; i<1; i++)
	{
		pp2[i] = nMatrix2[i];
	}
	PrintMatrixClockWisely(pp2, 1, 4);
	cout << endl;

	int nMatrix3[4][1] = {{1},{2},{3},{4}};
	int **pp3 = new int*[4];
	for (int i=0; i<4; i++)
	{
		pp3[i] = nMatrix3[i];
	}
	PrintMatrixClockWisely(pp3, 4, 1);
	cout << endl;

	int nMatrix4[2][5] = {1,2,3,4,5,6,7,8,9,10};
	int **pp4 = new int*[2];
	for (int i=0; i<2; i++)
	{
		pp4[i] = nMatrix4[i];
	}
	PrintMatrixClockWisely(pp4, 2, 5);
	cout << endl;

	system("pause");
	return 0;
}